River Acheron vs Greek mythology

River Acheron and Greek mythology both are nouns.

Word	Noun	Adjective	Verb	Adverb
River Acheron	Yes	No	No	No
Greek mythology	Yes	No	No	No

River Acheron (noun)	Greek mythology (noun)
(Greek mythology) a river in Hades across which the souls of the dead were carried by Charon	the mythology of the ancient Greeks